Tilting pad journal beatings are typically employed in turbine system constructions, with two bearings per rotor span a common arrangement. Bearings incorporating double tilting pads are also known.
Double tilting pad journal bearings are typically complex and difficult to manufacture in a cost effective manner. Generally, known bearing designs include milling and fitting operations during manufacture that give rise to complex manufacturing processes. For many of the existing bearing designs, special tools and equipment are required to incorporate the desired features. For example, the current double tilting pad bearing designs use hardened steel plates with spherical radii to accomplish the tilting of the pads. Generation of those radii, however, requires special equipment. Other designs use oil feed annuli on the sides of the beating casing which require special covers to seal in the oil. Some designs use end plates bolted onto the ends of the bearing casing with pins inserted through the plates into the bearing pads to prevent rotation of the pads. The use of these plates complicates the design by the addition of parts and related manipulative steps in the assembly process.
In many cases, special fixtures are required to accomplish the final boring of the bearing inner diameter. For example, though many beatings have an individual pad oil feed feature, the machining operations required to provide this feature are complex (radial and axial drilling operations) and do not, in any event, insure an even distribution of oil to the leading edge of the pads.
Some existing designs employ floating seal rings at the end of the bearing casing for oil flow control. This method leads, however, to higher power losses and higher operating temperatures for the bearing. Others use the relatively massive end plates for oil control and this can lead to hard scoring of the rotor.